title: Analyses of Ca2+ accumulation and dynamics in the endoplasmic reticulum of Arabidopsis root cells using a genetically encoded Cameleon sensor.
abstract: In planta, very limited information is available about how the endoplasmic reticulum (ER) contributes to cellular Ca(2+) dynamics and homeostasis. Here, we report the generation of an ER-targeted Cameleon reporter protein suitable for analysis of Ca(2+) accumulation and dynamics in the lumen of the ER in plant cells. Using stably transformed Arabidopsis (Arabidopsis thaliana) plants expressing this reporter protein, we observed a transiently enhanced accumulation of Ca(2+) in the ER in response to stimuli inducing cytosolic Ca(2+) rises in root tip cells. In all experimental conditions, ER Ca(2+) dynamics were substantially different from those monitored in the cytosol. A pharmacological approach enabled us to evaluate the contribution of the different ER-resident Ca(2+)-ATPase classes in the regulation of the ER Ca(2+) homeostasis. Taken together, our results do not provide evidence for a role of the ER as a major source that releases Ca(2+) for stimulus-induced increases in cytosolic Ca(2+) concentration. Instead, our results show that the luminal ER Ca(2+) elevations typically follow cytosolic ones, but with distinct dynamics. These findings suggest fundamental differences for the function of the ER in cellular Ca(2+) homeostasis in plants and animals.
authors.affiliation: Department of Biosciences, University of Milan, 20133 Milan, Italy.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Bonza
authors.forename: Giovanna
authors.initials: G
authors.lastname: Loro
authors.forename: Smrutisanjita
authors.initials: S
authors.lastname: Behera
authors.forename: Andrea
authors.initials: A
authors.lastname: Wong
authors.forename: Jörg
authors.initials: J
authors.lastname: Kudla
authors.forename: Alex
authors.initials: A
authors.lastname: Costa
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects; D007700:Kinetics; D018613:Microscopy, Confocal; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D059008:Time-Lapse Imaging / Q000379:methods
chemical_list: D002135:Calcium-Binding Proteins; D005456:Fluorescent Dyes; C495639:yellow cameleon; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium